I just put a K&N filter in my stock air box. On my 04rs and it sound really loud when it hit to 3-5000rpm. And my car is stock no exhaust or anything else just the filter. I wonder is that normal if it sound that loud (deep nosie) another question is do you guys think that going help me to gain some horsepower.

thanks

 

yes the loud rumble noise is normal. It is the natural sound of boxer engines. and It should help you gain some additional torque downlow.

 

If it's way louder than the OE filter then you'd better check to make sure you got the bottom edge of the filter box seated in the proper position. If you didn't (and it's easy to not get it seated) then your engine is sucking in unfiltered air and that's not good. If you have trouble getting the box together with the K&N then you may find it easier to remove the box completely from the car (2 nuts, one screw clamp and two hoses) and snap it together then remount the assembly just like at the factory.

 

What he said.

however the K&N will provide you with more intake roar than the factory filter.